Melotte 15 - The Heart of the Heart (wadeh237)

Melotte 15 - The Heart of the Heart

This is Melotte 15, the Heart of the Heart.

This image is a first for me in a couple of ways. It is my first Hubble palette narrow band image, and it is my first image processed from end to end entirely in PixInsight. There were two big processing challenges.

The first was that the sulphur data had an uncorrected gradient that was not present in the other two channels. It could have potentially been a problem with flat calibration, but that would be pretty rare. My flats tend to work pretty well. There was a large number of exposures, and when I went back to re-examine my pre-integration steps, I found that I included a number of subs in the sulphur channel that had clouds present. After I removed those, it was a bit better, but I still needed to use a few rounds of DBE in the sulphur channel. Since there is really no area of pure background anywhere in the frame, this took a while.

The second challenge was color balance. I struggled with this one for a long time. I tried using the color calibration process in PixInsight, but was never happy with the results. No matter what strategy I used, it insisted on badly black clipping the sulphur channel. I ultimately ended up doing a modest stretch with the ScreenTransferFunction process with the channels linked and applied it with HistogramTransformation. I then did multiple iterations of CurvesTransformation on individual color channels, with a bit of HistogramTransformation on each iteration to reset the black point. This gave me a reasonable color with minimal black clipping.

The gear used was:

Celestron EdgeHD8 with F/7 focal reducer

ASI1600MM-cool with Astrodon 3nm narrow band filters

Astro-Physics AP1100GTO-CP4

Exposures were 33x300 Ha, 102x300 OIII and 102x300 SII. The data was captured over 3 nights between 10/19 and 10/22 2018 (one of the nights was cloudy).

Original
Final
B

B

Description: This is a reprocess of The Heart of the Heart.

My wife wants a print of this one, and I was not happy with the original colors. This version has (in my opinion) better colors.

Uploaded: ...

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Status	Advanced success
Started	...
Astrometry.net job	3195235
PixInsight job	JA1X2CNBSBU7IAXIWKIWPTC2QHNYMNTC
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	02h34m58s.436
RA (top/left)	02h37m21s.609
RA (top/right)	02h32m30s.884
RA (bottom/right)	02h32m37s.453
RA (bottom/left)	02h37m23s.812

Dec (center)	+61°23′43″.12
Dec (top/left)	+61°37′47″.80
Dec (top/right)	+61°37′06″.72
Dec (bottom/right)	+61°09′30″.60
Dec (bottom/left)	+61°10′09″.18

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